The inhibition of premature vulcanization of vulcanizable rubber composition by using N-(thio)amides including hindered-alkylthio amides is known, for example, U.S. Pat. Nos. 3,546,185, 3,686,169, 3,780,001, 3,737,438, 3,849,418, 3,872,061 and British Pat. No. 1,345,144. 1,3-Di(1-chloro-1-nitropropylthio)imidazolidinetrione, (parabanic acid), is a known fungicide, U.S. Pat. No. 3,468,905.